A unidirectional tapered land thrust bearing cluster is disclosed in U.S. Pat. No. 5,829,338, issued to Chrestoff et al. FIG. 1 is a perspective view of the prior art thrust bearing. The single-piece thrust bearing 10 incorporates a plurality of bearing pads 12 evenly spaced around the circular thrust bearing 10.
Each of the bearing pads 12 in the thrust bearing 10 comprises an integral rectangular-shaped tapered section 14 and integral flat non-tapered section 16. Adjacent each bearing pad 12, the surface of the bearing cluster 10 is machined or otherwise profiled to provide the bearing pad 12 with an integral convergent lubricant path or slot 24. Each tapered section 14 has a tapered rise portion 18 that is the same at the outside diameter 20 as it is at the inside diameter 22 of the bearing 10. Each fluid feed slot 24 will facilitate the development of a hydrodynamic pressure zone along the length of the tapered rise portion 18.
As explained by Chrestoff et al., the thrust bearing 10 is designed for positioning under the back of a pump's swashplate, in a recess in the back plate of the pump. Counterclockwise rotation of the swashplate causes fluid to move from feed slots 24 to tapered rise portions 18 on the thrust bearing, thus forming a pressurized load carrying hydrodynamic film between the thrust bearing and swashplate, which opposes pressure exerted on the swashplate by the pump. Some of the fluid advances from the tapered rise portions 18 to narrow spaces between the flat sections 16 of the bearing, and the adjacent swashplate. In essence, a substantially continuous fluid buffer film is formed between the bearing 10 and adjacent swashplate, to reduce wear on the bearing caused by pump operation.
One disadvantage of the prior art thrust bearing is that the bearing fluid (which performs both cooling and lubricating functions) has not been ideally distributed in an axial direction during pump operation. Accordingly, the thrust bearings have more wear and damage at surface portions near their outer peripheries, than at surface portions near their inner peripheries. There is a need or desire for a thrust bearing which provides better distribution of fluid during pump operation, resulting in more even forces being applied across the bearing.